Thanks for your interest in the Intel® Edison platform.
I was investigating and I have not been able to find a Java library for the Nokia 5110 display, however, I found other libraries written in https://github.com/adafruit/Adafruit-PCD8544-Nokia-5110-LCD-library C/C++ and https://github.com/adafruit/Adafruit_Nokia_LCD Python (maybe you have already found them), so I suggest to take a look at them and try to write your Java library.
I have found this library for the https://github.com/sidwarkd/tessel-nokia5110 Nokia 5110 display that it may or may not work with the Edison board, however, you could test it. Additionally, I found this information to create a Java library that I believe you can find useful: http://stackoverflow.com/questions/6496597/how-can-i-develop-my-own-java-library http://stackoverflow.com/questions/6496597/how-can-i-develop-my-own-java-library.
Hope this information helps.